| Abstract: | Recent studies show that, in some seismogenetic areas, strong earthquakes occur rather predictably. Their pattern of occurrence, however, cannot be interpreted according to a classic model of seismic risk analysis. It is shown that semi-Markov models are capable of interpreting predictable behaviour and, in particular, the types suggested by the Slip Predictable Model, the Time Predictable Model and the Characteristic Earthquake Model. A number of general properties are demonstrated, dealing with return periods, waiting times, damage cost, stationary and variable characteristics of seismic risk analysis. The case of Friuli is then examined and its semi-Markovian interpretation is discussed. This interpretation is compared with others which also are possible, and the consequences for the computation of hazard and risk terms are evaluated. |
